For modular conveying belts, it is important to reduce the friction caused by the belt sliding over the support structure. This reduction in friction reduces the power required to drive the belt and at the same time reduces the wear on the modular belt. For this purpose low friction, plastic wear guides or wear strips are fixed to the support structure and provide the support surface for the belt. Wear guides are usually constructed of extruded or machined plastic profiles, and various profile shapes are used. The most common shapes are flat strips that are bonded or screwed to the metal support. As shown in FIG. 1, labeled prior art, the plastic guides 10 may be joined to a metal profile 13 (C-shape or U-shape) by shifting the plastic guide 10 longitudinally into the metal profile 13. Some specific arrangements using specialized frame profiles are disclosed in U.S. Pat. Nos. 5,137,145; 5,186,314; 6,848,572; and 4,961,492. As shown in FIGS. 2A and 2B, there have also been wear strips 16 with a C-shape or U-shape that are fixed to a flat metal strip 19 by pressing the wear strip onto it in the direction of arrow 20. This solution typically requires additional fasteners (at least one per profile section) in order to prevent the profile from slipping off the metal strip 19.
There is a need for U-shaped plastic wear guides in applications where it is essential for the running belt to be prevented from flipping up or lifting during operation. This risk is particularly significant for radius belts and chains when running through a curve. In the curve, radial forces are pressing the chain or belt against the inner guide.
The prior art solutions discussed above are generally costly to produce and in some cases difficult to install. The issues with installation are particularly relevant for long guide profiles that have to be shifted along the entire length of the metal profile. Also, with a curved profile, installation is even more difficult. In order to provide for easier installation, it is usually necessary to provide some clearance between the metal channel and the plastic guide profile. However, this space may lead to unwanted vibration when the belt slides along the plastic guide profile.
The prior art version shown in FIGS. 2A and 2B also does not fulfill all of the desired requirements with respect to accuracy and rigidness because the plastic profiles of that shape tend to distort during installation and may require additional pins and screws to be secured to the flat steel. These additional components result in additional work and cost.
Accordingly, there is a need for an improved design that is economical, easy to install, and that prevents the running belt from flipping up or lifting during operation.